The amount of fuel injected by a fuel injector into a combustion chamber is a function of a fuel system supply or rail pressure, a cylinder or combustion chamber pressure, and an interval during which the fuel injector remains open, which is called the on-time. A conventional approach to determine the fuel injector on-time given a desired fuel quantity and a fuel system pressure is to use a predetermined two dimensional look-up table with fuel system, fuel rail, or common rail pressure and desired fuel quantity as independent variables or parameters and the fuel injector on-time as a dependent variable.
The challenge with the conventional approach is that the pressure profile in the fuel system may change with respect to a look-up table calibration or reference, thus changing the actual volume, amount or quantity of delivered fuel. Factors that may change the pressure profile include pressure waves in the fuel system, fuel rail, or common rail, engine speed, a start-of-injection (SOI) designed as a function of inputs other than fuel system pressure and desired fuel quantity, and fuel system pressure set-point changes.